1. Technical Field
The present invention relates to a multi-layered capacitor, and more particularly, to a multi-layered capacitor mounted with a vibration preventing device.
2. Description of the Related Art
In general, a multi-layered ceramic capacitor (MLCC) is a chip type capacitor that is mounted on a printed circuit board of various electronic products, such as mobile communication terminals, notebooks, computers, and personal digital assistants (PDAs), to perform an important role of charging or discharging electricity and has various sizes and multi-layered types according to the usage and capacity thereof.
In general, the multi-layered ceramic capacitor has a structure in which an internal electrode is alternately multi-layered between a plurality of dielectric layers.
The multi-layered ceramic capacitor can achieve advantages, such as miniaturization and implementation of high capacity, easiness of mounting, and therefore has been widely used as a component of various electronic devices.
As a ceramic material forming an element of the multi-layered ceramic capacitor, a ferroelectric material, such as barium titanate, having relatively high dielectric constant has been generally used. Since the ferroelectric material has piezoelectricity and electrostrictive property, when electric field is applied to the ferroelectric material, stresses and mechanical deformations are shown as vibrations, which are delivered to a circuit board side from a terminal electrode of the multi-layered ceramic capacitor to a circuit board side.
That is, when alternating voltage is applied to the multi-layered ceramic capacitor, stresses Fx, Fy, and Fz are generated in an element body of the multi-layered ceramic capacitor according to each direction and vibrations are generated accordingly. These vibrations are delivered from the terminal electrode to the circuit board, such that the overall circuit board becomes an acoustic radiating surface and a vibrating sound that is noise is generated.
In the vibrating sound, the vibrating sound in an audible frequency band (20 to 20000 Hz) is problematic, which should be essentially solved.
Recently, in order to solve the problem due to the vibrating sound, technologies for preventing vibrations by elastically deforming an external terminal of the multi-layered ceramic capacitor have been introduced.
In addition, as disclosed in Korean Patent Laid-Open Publication No. 10-2010-0066080, various technologies, such as a technology for using a separate component to suppress a propagation of vibrations generated due to piezoelectric and electrostrictive properties and reduce a generation of noise and a technology of forming circuit board holes around a mounted multi-layered ceramic capacitor to suppress vibrations of a circuit board, have been introduced; however, these technologies require a separate process and cannot sufficiently obtain the sufficient anti-vibration effect compared to the complexity of the process. Therefore, a technology of prevent vibrations with a simpler structure has been urgently required.